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EC Number

Catalytic Site Atlas

CSA LITERATURE entry for 1l6p

E.C. nameprotein-disulfide reductase
SpeciesEscherichia coli (Bacteria)
E.C. Number (IntEnz)
CSA Homologues of 1l6p1jpe,1jzd,1se1,1vrs,1z5y,
CSA Entries With UniProtID P36655
CSA Entries With EC Number
PDBe Entry 1l6p
PDBSum Entry 1l6p
MACiE Entry 1l6p

Literature Report

IntroductionThe N terminal region of the thioloxidoreductase enzyme DsbD from E.coli is able to reduce the disulphide bond in DsbC thus participates in the pathway whereby electrons from NADPH are used to break incorrectly formed disulphides in proteins in the periplasm. It displays a unique Ig fold, but still shows homology with the thioloxidoreductase family.
MechansimCys 109 is the primary nucleophile that attacks the intramolecular disulphide to form a disulphide between DsbD and DsbC. Cys 103 then acts as a secondary nucleophile to reduce this disulphide, activated by a Asp 68-Tyr 42 diad which acts as a proton relay system. This results in the reduced form intermediate, stabilised by contacts with Tyr 71 and Phe 70

Catalytic Sites for 1l6p

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
CysA109128macie:sideChainActs as primary nucleophile to break the intramolecular disulphide bond in DsbC which leads to the reduced form tof the enzyme with an intramolecular disulphide bond between Cys 109 and 103.
CysA103122macie:sideChainActs as nucleophile to reduce disulphide bond between DsbC and DsbD, forming the reduced intermediate.
TyrA4261macie:sideChainActs to deprotonate Cys 103 thus allowing it to form the intramolecular disulphide with Cys 109 that characterises the reduced form of the enzyme.
AspA6887macie:sideChainActivates Tyr 42 to allow it to act as a general acid-base, thus is part of an Asp-Tyr diad which functions as a proton relay system to activate Cys 103.
TyrA7190macie:sideChainActs to shield the reduced form from nucleophilic attack, thus stabilising it.
PheA7089macie:sideChainMakes hydrophobic contact with intramolecular disulphide of reduced form to stabilise it by preventing nucleophilic attack by a water molecule.

Literature References

Notes:The pdb file refers only to the N terminal domain of the protein.
Goulding CW
Thiol-disulfide exchange in an immunoglobulin-like fold: structure of the N-terminal domain of DsbD.
Biochemistry 2002 41 6920-6927
PubMed: 12033924
Haebel PW
The disulfide bond isomerase DsbC is activated by an immunoglobulin-fold thiol oxidoreductase: crystal structure of the DsbC-DsbDalpha complex.
EMBO J 2002 21 4774-4784
PubMed: 12234918